Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$131.85	7.762%	$142.0842	$142.08	$142.10	$142.10
Purchase #2	$207.90	6.785%	$222.006	$222.01	$222.00	$222.00
Purchase #3	$186.96	6.226%	$198.6001	$198.60	$198.60	$198.60
Purchase #4	$137.60	13.306%	$155.9091	$155.91	$155.90	$155.90
Purchase #5	$137.25	5.734%	$145.1199	$145.12	$145.10	$145.10
Purchase #6	$28.89	3.780%	$29.982	$29.98	$30.00	$30.00
Purchase #7	$147.80	13.171%	$167.2667	$167.27	$167.25	$167.30
7 purchase totals =	$978.25		$1,060.9680	$1,060.97	$1,060.95	$1,061.00